Effect of phosphate compound on the reduction of the pressure drop of laboratory-scale fabric filter.

Fabric filters are generally used to eliminate the particulate matter of flue gas that is generated from waste incinerators. The pressure drop of fabric filter (ΔP) is accompanied by the build-up of a dust layer on the fabric filter, and ΔP increase leads to an increase in the energy consumption of induced draft fan in an incineration facility. In this study, phosphoric acid (H3PO4) and monobasic calcium phosphate (Ca(H2PO4)2) are tested as chemicals to reduce ΔP in fabric filter using a laboratory-scale equipment. The phosphorus concentration of collected dust was correlated to the increment of ΔP per unit weight of dust deposited on the filter fabric. The effect on ΔP reduction was apparent at the phosphorus concentrations of 2.2-5.3 wt% in the collected dust. As a result, the gas permeability was enhanced by 2-6 times as compared to that was observed at phosphorus concentrations less than 0.6 wt%. Based on the result of XRD analysis of the dust sampled from the filer bag, it was concluded that H3PO4 reacted with the Ca compounds even though Ca-P compound could not be identified exactly. When H3PO4 was sprayed, dust particles grew in size and the surface roughness of dust layer increased too. Such changes in the physicochemical properties of dust seemed to enhance the gas permeability of the dust layer, which caused a reduction in the value of ΔP.